Glad my experience helps.
I hope this is useful too;
two 4 acre fields, almost identical - same aspect, soil etc, (They were one larger origionally but I split it).
Neither receives any fertilizer other than the sheeps own droppings and clover in the sward.
12 Hebs cannot eat the grass as fast as it grows in summer - and they can out winter on it all winter and come April their is still grass ahead of them - No supliment feeding unless its snow covered.
The same field can take 10 mules but they eat the grass faster than it grows and I need to take them out to another field after 6-8 weeks. In winter, they finish the grass by Mid Jan.
If I fertilized the fields I could up production by 30-40% however I intend to use Clover to up production by 20% instead, as I consider it more sustainable.
Hebs are lightweight and if you find buyers for the meat, they are good.
I have also found if you tell the market your taking them they let buyers know, so you actually get good prices for them